A 27-year-old Japanese man visited our urological department due to urinary frequency, and we detected a ureterocele by cystoscopy. The treatment consisted of an endoscopic-laser incision of the ureterocele. After the operation, the patient’s symptoms subsided, and the vesicoureteral reflux and urinary infection disappeared. With the advances in image diagnostic technology, a ureterocele is easily diagnosed during childhood. In the present case, the ureterocele may have increased in volume over a period of decades, causing the urinary frequency. An endoscopic incision is the standard treatment for ureterocele, but there are concerns about vesicoureteric reflux after the endoscopic-laser incision, the patient is still doing well. The present case indicates that endoscopic-laser incision is an effective treatment for a ureterocele, at least in adult patients.